The rotating machine used as a synchronous motor or generator has a salient pole rotor and a stator surrounding an outer circumference of the salient pole rotor with a predetermined interval. The salient pole rotor has a disk-shaped spoke installed to an outer circumference of an axial center of its rotation shaft and a cylindrical rib having an inner circumferential surface integrally installed to an outer circumference of the spoke. A plurality of salient poles are formed on an outer circumferential surface of the rib in a radial shape and are arranged in parallel along an axial direction of the rotation shaft. In addition, field coils are wound around each of the salient poles.
As one of the cooling methods of the rotating machine, a ventilation cooling type is employed, in which the cooling air is fed from one end side of the axial direction of the salient pole rotor (for example, see Patent Document 1).
Typically, the salient pole rotor and the stator surrounding the outer circumference of the salient pole rotor are provided inside the closed frame. A ventilation fan is provided to one end side of the rotation shaft of the salient pole rotor inside this frame, so that the air is fed in a radial direction as the rotation shaft is rotated. The air blowing by the fan is sent to the opposite end of the salient pole rotor through a cooler provided between an inner surface of the closed frame and an outer surface side of the stator and flows to the stator and the salient pole rotor along the axial direction from the opposite end (one end side).
The cooling air blowing as described above cools a coil end of the stator, flows between the stator and the salient pole rotor, and is then pushed to spaces between a plurality of salient poles provided to the outer circumferential surface of the rib described above. In addition, the cooling air flows through the spaces in the axial direction to cool each salient pole and arrives at an inlet side of the aforementioned ventilation fan. Furthermore, a part of the air flowing between the stator and the salient pole rotor flows to the outer side of the stator through a ventilation duct provided in a radial direction of the stator core and then similarly arrives at the inlet side of the aforementioned ventilation fan.
In this ventilation type, the cooling air flows from one end side of the salient pole rotor to the stator and the salient pole rotor along the axial direction. Therefore, the temperature of the rotating machine increases from the aforementioned one end side to the opposite side end and reaches its maximum in this opposite side. That is, in the ventilation cooling type of the prior art, the air flows to the heating portion of the rotating machine (including the stator and each salient pole of the salient pole rotor) in a single direction. Therefore, a temperature distribution becomes irregular.